At a certain point my right testicle appears to be attatched to the skin of the sack in a way that the other is not. There is no lump as such; it feels more like a soft indentation. At this point the skin is of a much lighter colour and there is a small purple vein. The testicle has been like this for a year or so and occasionally causes me very mild pain but there has been no significant change in the condition in this time. Is this anything to worry about or something normal (or harmless). Thanks in advance.

Unfortunately, it is impossible to "diagnose" over the internet. You see, we don't have access to your medical records, nor can we examine you. Have you brought this to the attention of your doctor? If not, I suggest you do so.